Low contrast highlight removal?

Been reading for a long time and always found an answer to my inquiries here, but can't find any effective solutions for my problem:

Attached is a still from a sequence of which the glass with shadow rolls over the backdrop-overlap which, due to amateurish neglect, produces a severe highlight from the lightning. Camera tracks the glass. I would like to remove this highlighted line, but been struggling for hours upon hours with clone tool and animating, with absolutely unbearable results due to all the movement. Feel like it should be possible to animate a mask to follow line which somehow could calculate pixels, but hey! I could well be spoiled by all modern retouching craziness.

First off: My problem with the clone tool was that as mentioned, camera tracks the glass, the shadow cast from the glass is warping as the glass rolls and the refractions of the glass itself distorts the line in such a way that I, if I did it correctly, got too many slight shifts and changes within the clone-mask.

Then, to your alpha matte-approach, the goal is to isolate the highlighted line or have I misunderstood?